Method of producing modified polyester moulded articles, and said moulded articles

ABSTRACT

A method of producing modified polyester moulded articles which is characterized in that, when producing moulded articles from a modified polyester composition comprising a polyester composed of an acid component chiefly consisting of aromatic dicarboxylic acid and glycol component chiefly consisting of aliphatic diol, and a modified polyolefin, there is incorporated an ethylene-acrylate copolymer; together with the moulded articles produced thereby.

BACKGROUND OF THE INVENTION

The present invention relates to a method of producing modifiedpolyester moulded articles and to the moulded articles obtained thereby.The objective thereof lies in offering a method of producing mouldedarticles which, while still maintaining their low-temperature impactresistance or moist heat resistance, are also outstanding in theirinjection moulding and extrusion moulding properties and, furthermore,even when deformed do not undergo phase separation or fibrillation;together with the moulded articles formed thereby.

On account of their outstanding chemical and mechanical properties,polyesters have long been widely used in applications of various kindssuch as fibres, films, industrial resins and bottles. These polyestershave in recent years come to be used under severe conditions, not justfor motor vehicle and electrical/electronic components in particular,but also for industrial applications in general. In such applications,conventional polyesters have inadequate low-temperature impactresistance and they are susceptible to hydrolysis under high humidityand high temperature conditions, so there have been restrictions ontheir use.

For the improvement of the low-temperature impact strength of polyesterresins, there has to some extent been employed the incorporation ofcore/shell type impact absorbing agents in which a rubber or the like isused as one component, or the incorporation of a modified polyolefinhaving functional groups which react with the polyester terminals.

On the other hand, in regard to the hydrolysis of polyesters, it haslong been known that this problem is promoted by terminal carboxylgroups and, in order to overcome it, there are methods such assuppressing the terminal carboxyl group concentration by low-temperaturemelt polymerization and solid phase polymerization, or by adding acompound which reacts with the terminal carboxyl groups such as alkalinecompounds, diglycidyl terephthalate, polycarbodiimide, ethylenecarbonate and imidazoline compounds. Of these methods, some have alreadybeen employed on a practical basis. However, with an approach based onthe method of polymerization, productivity is inevitably sacrificed tosome extent, while in the case where a reactive compound is added,problems arise such as the adverse effects caused by the low molecularweight materials produced as a result of the reaction or decompositionat the time of melt fabrication, and so further improvements aredemanded in relation to applications where used under more severeconditions.

In order to resolve such problems, there is known the incorporation of apolyolefin which has been modified by means of glycidyl groups or thelike, so as to reduce the terminal carboxyl groups concentration byreaction therewith and, furthermore, so as to reduce the viscosity atthe time of melt fabrication. In such circumstances, if, for example, anethylene-alkylÿacrylate-glycidyl terpolymer is used in order to lowerthe glass transition point at the same time, or to further increase thecompatibility with the polyester, the acrylate partially decomposesduring the melt fabrication and carboxyl groups are newly produced,which then promote the polyester hydrolysis. In order to prevent such aproblem, the modified polyolefin has to be restricted to anethylene-glycidyl copolymer which is not a terpolymer containing alkylacrylate. However, when an ethylene-glycidyl copolymer is used, whilethere is reaction with the molecular terminals of the polyester, thereis inadequate compatibility between the polyethylene regions and thepolyester, and phase separation occurs when the moulded article issubjected to bending or other such repeated deformation during use. Incertain circumstances, fibrillation occurs, so that not only is theappearance of the moulded article impaired but the product performanceis also lowered, and so a resolution of this difficulty has beendemanded.

SUMMARY OF THE INVENTION

As a result of a painstaking investigation aimed at obtaining mouldedarticles which, while maintaining their low-temperature impactresistance and moist heat resistance, are also resistant to flexuralfatigue, the present inventors have discovered that this objective isrealised by incorporating an ethylene copolymer at the same time as theglycidyl copolymer, and it is on this discovery that the presentinvention is based.

The present invention is a method of producing modified polyestermoulded articles which is characterized in that, when producing mouldedarticles from a modified polyester composition comprising a polyestercomposed of an acid component chiefly consisting of aromaticdicarboxylic acid and a glycol component chiefly consisting of aliphaticdiol, and a modified polyolefin, there is incorporated anethylene-acrylate copolymer; together with the moulded articles producedthereby.

In the present invention, ‘polyester’ is a polyester composed of an acidcomponent chiefly consisting of aromatic dicarboxylic acid and a glycolcomponent chiefly consisting of aliphatic diol. As examples of the‘aromatic dicarboxylic acid’, there are terephthalic acid, naphthalenedicarboxylic acid, isophthalic acid, diphenyl dicarboxylic acid,diphenyl ether dicarboxylic acid, diphenyl sulphone dicarboxylic acidand diphenyl ketone dicarboxylic acid. As examples of the ‘aliphaticdiol’, there are ethylene glycol, trimethylene glycol, tetramethyleneglycol and hexamethylene glycol. Here, ‘chiefly’ is not particularlyrestricted but broadly means 80 mol %. Other acid component or hydroxycomponent may be copolymerized within a range below 20 mol %. Again,there can also be used a polyfunctional compound with three or morefunctional groups, within a range such that the polyester remainssubstantially linear. Amongst the aforesaid polyesters, polyethyleneterephthalate, polyethylene naphthalate and polybutylene terephthalateare preferred. Such polyester is produced by a conventional meltpolymerization method but, where required, may also be based on a solidphase polymerization method.

In the present invention, ‘modified polyolefin’ is a polyolefin whichhas undergone graft- or co-polymerization with an unsaturated epoxide orderivative thereof. A polyolefin which is a graft- or co-polymer of anunsaturated acid or anhydride or other derivative thereof, although itis a modified polyolefin nevertheless lies outside the scope of thisinvention. The reason for this is because the carboxyl groups producedas a result of reaction with the polyester will promote the hydrolysisof the polyester. As specific examples of modified polyolefins whichhave been modified by means of an unsaturated epoxy, there areethylene-glycidyl copolymer, propylene-glycidyl terpolymer,butylene-glycidyl copolymer and the like. Of these, the terpolymer hasinferior heat resistance compared to the copolymers, so the copolymersare preferred and ethylene-glycidyl copolymer is particularly preferred.These are polymerized by conventional methods.

In the present invention, the proportion of the polyester compositionrepresented by said modified polyolefin will differ depending on theapplication but, normally, it is no more than 30 wt % and preferably nomore than 20 wt %.

In the present invention, ‘ethylene-acrylate’ copolymer is a copolymerchiefly comprising ethylene units in which there are also alkyl acrylateester units. The ethylene content is at least 60% and preferably atleast 70%. Furthermore, the alkyl ester will have no more than 8 carbonsand preferably no more than 4 carbons, specific examples being themethyl, ethyl and butyl esters. Of these, copolymers such asethylene-methyl acrylate and ethylene-butyl acrylate can be cited aspreferred examples.

In the present invention, the amount of ethylene-acrylate copolymer ispreferably from 3 to 40 wt % in terms of the modified polyolefin. Ifthere is less than 3 wt %, then there is little effect in terms ofpreventing phase separation, while if there is more than 40 wt % theheat resistance of the polyester may be lowered. A part of theethylene-acrylate copolymer may undergo thermal decomposition and themoist heat degradation of the polyester may be promoted as a result ofthe carboxyl terminal groups produced, so it is preferred that as littleas possible be employed. From 5 to 35 wt % is further preferred.

The reason why the flexural fatigue resistance is enhanced whilemaintaining the low-temperature impact resistance and the moist heatdegradation resistance by the joint use of an ethylene-glycidylcopolymer and an ethylene-acrylate copolymer along with the polyester,is not clear. However, it is assumed that, since ethylene-acrylatecopolymers have inferior thermal stability than ethylene-glycidylcopolymers, but have superior heat resistance compared toethylene-acrylate-glycidyl terpolymers, by combining anethylene-glycidyl copolymer and an ethylene-acrylate copolymer, themoist heat resistance is simultaneously improved while still maintainingthe low-temperature impact resistance and the compatibility at theethylene-acrylate-glycidyl terpolymer level.

There may be freely included in the composition of the presentinvention, known antioxidants, thermal decomposition preventives,ultraviolet absorbers, hydrolysis resistance improvers, colouring agents(dyes and pigments), antistatic agents, electro-conductors,crystallization nucleating agents, crystallization promoters,plasticizers, ready slip agents, lubricating agents, release agents,flame retardants, flame retarding auxiliaries and reinforcing fillers(glass fibre, glass beads, carbon fibre, aramid fibre and the like)within a range such that the characteristics of the present inventionare not impaired. For example, in the case of a reinforcing filler, itis necessary to take care that the surface treatment agent thereof orthe converging agent be selected such that the objectives of theinvention are not impaired.

In the present invention, ‘moulded article’ refers to an injectionmoulded article or extrusion moulded article. As examples of injectionmoulded articles, there are ordinary electrical/electronic componentsand automobile components. As examples of melt extruded articles, thereare fibres, films, sheets, tubes and pipes, etc.

In regard to the composition of the present invention, carrying out themoulding with the polyester and modified polyolefin and/orethylene-acrylate copolymer already melt-blended will have aconsiderable effect in terms of preventing phase separation but, fromthe point of view of the heat resistance and moist heat resistance ofthe polyester moulded articles, the less the thermal history the better,so it is preferred that direct extrusion moulding be carried out using ascrew of a type provided at its tip with a Dulmage or Maddock mixingzone. Of course, it is also possible to supply each component to themoulding machine and then carry out direct injection moulding.

EXAMPLES

Below, the present invention is explained in more specific terms bymeans of examples, but it goes without saying that the present inventionis not to be restricted just to these. Now, in the examples ‘parts’ and‘%’ mean parts by weight or percentage by weight respectively. Thevarious properties in these examples were measured by the followingmethods.

(1) MFR (units: g/10 minutes)

Based on ISO 1133, measurements were carried out at 190° C. under a 2.16kg load.

(2) Intrinsic viscosity

This was calculated from the solution viscosity measured at 35° C. usinga mixed solvent comprising phenol/tetra-chloroethane (weight ratio60/40).

(3) Terminal carboxyl group concentration

This was measured by the method of A. Conix (Makromol. Chem. Volume 26,page 226)

(4) Low-temperature impact resistance

The Charpy impact strength of a notched test piece was measuredmaintained at −40° C., based on ISO179.

The various resins employed in this invention were as follows.

A-1: ethylene-glycidyl methacrylate copolymer of MFR 5 containing 8%glycidyl methacrylate

A-2: ethylene-glycidyl methacrylate terpolymer of MFR 6 containing 8%glycidyl methacrylate and 28% methyl acrylate.

B-1: polyethylene in which 9 wt % of methyl acrylate has beencopolymerized, of MFR 2.

B-2: polyethylene in which 28 wt % of methyl acrylate has beencopolymerized, of MFR 7.

B-3: polyethylene in which 17 wt % of butyl acrylate has beencopolymerized, of MFR 7.

Examples 1 and 2, Comparative Examples 1 to 3

Aforesaid resins A and B were mixed with polybutylene terephthalate(hereinafter abbreviated to PBT) of intrinsic viscosity 0.8 and terminalcarboxyl group concentration 30, in proportions, by weight ratio, ofPBT/A-1/B-3=95/5/0 (sample a, Comparative Example 1), 95/4/1 (sample b,Example 1), 95/2/3 (sample c, Comparative Practical Example 2) andPBT/A-2/B-3=95/4/1 (sample d, Comparative Example 2), after which aninjection moulding machine of mould clamping force 80 tons, which wasset at 230-250° C., was used to mould test pieces for impact testing andtest pieces with a hinge region. In regard to the low-temperature impactvalues, those for samples a, b, c and d were all around 8 to 10 KJ/m2,and were superior to the PBT blank in which A and B were notincorporated (2 KJ/m2, Comparative Example 3). However, when a flex testwas conducted 2000 times at room temperature, whereas there was nodifference in samples b, c and d, in the case of sample a slight phaseseparation was noted in the hinge region. Again, whereas the percentagestrength retention after 100 hours treatment in boiling water was 95%for sample b and 90% for sample c, that for sample d was lowered to 87%.For comparison, the level of retention in the case of PBT in which,A andB were not incorporated was only 80%.

Examples 3 and 4, Comparative Example 4

Aforesaid components A and B were supplied relative to polyethyleneterephthalate (hereinafter abbreviated to PET) of intrinsic viscosity1.0 and terminal carboxyl group concentration 10 to give proportions ofPET/A-1/B-1=95/5/0 (sample e, Comparative Example 4), 95/4/1 (sample f,Example 3) and PET/A-1/B-2=95/4/1 (sample g, Example 4), then extrusioncarried out by means of an extruder with a screw with a Dulmage typekneading zone at the tip, and after drawing at a draw factor of 92% ofthe maximum draw ratio, a 3% relaxation heat treatment was carried outand there was obtained 1500 denier/192 filament multifilament yarn. Whenthe multifilament yarns were subjected to a moist heat degradationtreatment in a sealed tube, the percentage strength retention after 48hours was good at about 95% for samples e and f, and 90% for sample g.However, when a bending endurance test was carried out 500 times at roomtemperature, with sample e there was about 30% fibrillation, whereaswith sample f and sample g it was merely 5% and 1% respectively, sooutstanding flexural fatigue resistance was shown.

As explained above, in the present invention, by incorporating anethylene-glycidyl copolymer and ethylene-acrylate copolymer into thepolyester, it is possible to obtain moulded articles which, whilemaintaining low-temperature impact resistance and moist heat resistance,do not exhibit phase separation or fibrillation with repeateddeformation and have a good appearance and durability.

What is claimed is:
 1. A method of producing a modified polyestermoulded article comprising molding a modified polyester compositionconsisting essentially of component (a) a polyester made from an acidcomponent containing at least 80 mol % of aromatic dicarboxylic acid anda glycol component containing at least 80 mol % of an aliphatic diol,component (b) an ethylene-glycidyl copolymer and component (c)consisting of 5-35 weight percent based on the ethylene-glycidylcopolymer of an ethylene-acrylate copolymer that does not containcomonomers other than ethylene and alkyl acrylate comonomers, whereinthe combination of the ethylene-glycidyl copolymer and theethylene-acrylate copolymer is no more than 5 weight percent based onthe modified polyester composition.
 2. A method of producing themodified polyester moulded article according to claim 1, wherein theethylene-glycidyl copolymer is an ethylene-glycidyl methacrylatecopolymer.
 3. A method of producing the modified polyester mouldedarticle according to claim 1, wherein the alkyl groups of the alkylacrylate comonomers each independently contain 1 to 8 carbon atoms.
 4. Amethod of producing the modified polyester moulded article according toclaim 1, wherein the alkyl groups of the alkyl acrylate comonomers eachindependently contain 1 to 4 carbon atoms.
 5. A method of producing themodified polyester moulded article according to claim 1, wherein themoulded article of claim 1 is moulded by an injection moulding method ormelt extrusion method.
 6. A modified polyester moulded article preparedaccording to claim 5, wherein the melt extruded moulded article is inthe form of fibre, film, sheet, tube or pipe.
 7. A method of producing amodified polyester molded article according to claim 1, wherein the acidcomponent is a diphenyl dicarboxylate acid, a diphenyl etherdicarboxylic acid, a diphenyl sulphone dicarboxylic acid, or a diphenylketone dicarboxylic acid.
 8. A method of producing the modifiedpolyester molded article according to claim 1, comprising injectionmolding the molded article in an injection molding machine of moldclamping force 80 tons set at 230-250° C.
 9. A method of producing themodified polyester molded article according to claim 1, comprisingextrusion molding the molded article with a screw with a kneading zoneat the tip, drawing at a draw factor of 92% of the maximum draw ratio,and afterwards carrying out a relaxation heat treatment.
 10. A method ofproducing the modified polyester molded article according to claim 1,wherein the molded article is a 1500 denier/192 filament multifilamentyarn.
 11. A modified polyester composition consisting essentially ofcomponent (a) a polyester made from an acid component containing 80 mol% of an aromatic dicarboxylic acid and a glycol component containing 80mol % of aliphatic diol, component (b) a modified polyolefin andcomponent (c) consisting of 5-35 weight percent based on the modifiedpolyolefin of an ethylene-acrylate copolymer that does not containcomonomers other than ethylene and alkyl acrylate comonomers, whereinthe combination of the modified polyolefin and the ethylene-acrylatecopolymer is no more than 5 weight percent based on the modifiedpolyester composition.
 12. A modified polyester composition according toclaim 11, wherein the polyester is polybutylene terephthalate.
 13. Amodified polyester composition according to claim 11, wherein thepolyester is polyethylene terephthalate.
 14. A modified polyestercomposition according to claim 11, wherein the alkyl groups of the alkylacrylate comonomers each independently contain 1 to 8 carbon atoms. 15.A modified polyester composition according to claim 11, wherein thealkyl groups of the alkyl acrylate comonomers each independently contain1 to 4 carbon atoms.
 16. A modified polyester composition according toclaim 11, wherein the alkyl groups of the alkyl acrylate comonomers eachindependently are methyl, ethyl or butyl.
 17. A modified polyestercomposition according to claim 16, wherein the alkyl groups of the alkylacrylate comonomers are methyl groups.
 18. A modified polyestercomposition according to claim 16, wherein the alkyl groups of the alkylacrylate comonomers are butyl groups.
 19. A modified polyestercomposition according to claim 11, wherein the modified polyestercomposition has no more than 5% fibrillation after conducting a bendingendurance test 500 times at room temperature.
 20. A modified polyestercomposition according to claim 11, wherein the modified polyestercomposition has a percentage strength retention of at least 95% after100 hours of treatment in boiling water.
 21. A modified polyestercomposition consisting of a polyester made from an acid componentcontaining 80 mol % of an aromatic dicarboxylic acid and a glycolcomponent containing 80 mol % of aliphatic diol, 4 weight % of anethylene-glycidyl methacrylate terpolymer and 1 weight % of anethylene-acrylate copolymer that does not contain comonomers other thanethylene and alkyl acrylate comonomers, wherein the weight percent isbased on the weight of the modified polyester composition.
 22. A methodof producing a modified polyester molded article comprising molding amodified polyester composition consisting of a polyester made from anacid component containing at least 80 mol % of aromatic dicarboxylicacid and a glycol component containing at least 80 mol % of an aliphaticdiol, an ethylene-glycidyl copolymer, and 5 to 35 weight percent basedon the ethylene-glycidyl copolymer of an ethylene-acrylate copolymerthat does not contain comonomers other than ethylene and alkyl acrylatecomonomers, wherein the combination of the ethylene-glycidyl copolymerand the ethylene-acrylate copolymer is no more than 5 weight percentbased on the modified polyester composition.
 23. A modified polyestercomposition consisting of a polyester made from an acid componentcontaining 80 mol % of an aromatic dicarboxylic acid and a glycolcomponent containing 80 mol % of aliphatic diol, an ethylene-glycidylcopolymer and 5 to 35 weight percent based on the an ethylene-glycidylcopolymer of an ethylene-acrylate copolymer that does not containcomonomers other than ethylene and alkyl acrylate comonomers, whereinthe combination of the ethylene-glycidyl copolymer and theethylene-acrylate copolymer is no more than 5 weight percent based onthe modified polyester composition.
 24. A modified polyester compositionconsisting of a polyester made from an acid component containing 80 mol% of an aromatic dicarboxylic acid and a glycol component containing 80mol % of aliphatic diol, a modified polyolefin and 5 to 35 weightpercent based on the modified polyolefin of an ethylene-acrylatecopolymer that does not contain comonomers other than ethylene and alkylacrylate comonomers, wherein the combination of the modified polyolefinand the ethylene-acrylate copolymer is no more than 5 weight percentbased on the modified polyester composition.
 25. A method of producing amodified polyester moulded article comprising molding a modifiedpolyester composition consisting essentially of component (a) apolyester made from an acid component containing at least 80 mol % ofaromatic dicarboxylic acid and a glycol component containing at least 80mol % of an aliphatic diol, component (b) an ethylene-glycidyl copolymerand component (c) 5-35 weight percent based on the ethylene-glycidylcopolymer of polyethylene into which only alkyl acrylate has beencopolymerized, wherein the combination of the ethylene-glycidylcopolymer and the ethylene-acrylate copolymer is no more than 5 weightpercent based on the modified polyester composition.
 26. A modifiedpolyester composition comprising of component (a) a polyester made froman acid component containing 80 mol % of an aromatic dicarboxylic acidand a glycol component having 80 mol % of aliphatic diol, component (b)a modified polyolefin and component (c) 5-35 weight percent based on themodified polyolefin of polyethylene into which only alkyl acrylate hasbeen copolymerized, wherein the combination of the modified polyolefinand the ethylene-acrylate copolymer is no more than 5 weight percentbased on the modified polyester composition.
 27. A modified polyestercomposition comprising a polyester made from an acid componentcontaining 80 mol % of an aromatic dicarboxylic acid and a glycolcomponent containing 80 mol % of aliphatic diol, 4 weight % of anethylene-glycidyl methacrylate terpolymer and 1 weight % of polyethyleneinto which only alkyl acrylate has been copolymerized, wherein theweight percent is based on the weight of the modified polyestercomposition.
 28. A method of producing a modified polyester moldedarticle comprising molding a modified polyester composition consistingof a polyester made from an acid component containing at least 80 mol %of aromatic dicarboxylic acid and a glycol component containing at least80 mol % of an aliphatic diol, an ethylene-glycidyl copolymer, and 5 to35 weight percent based on the ethylene-glycidyl copolymer ofpolyethylene into which only alkyl acrylate has been copolymerized,wherein the combination of the ethylene-glycidyl copolymer and theethylene-acrylate copolymer is no more than 5 weight percent based onthe modified polyester composition.
 29. A modified polyester compositionconsisting of a polyester made from an acid component containing 80 mol% of an aromatic dicarboxylic acid and a glycol component containing 80mol % of aliphatic diol, a ethylene-glycidyl copolymer and 5 to 35weight percent based on the ethylene-glycidyl copolymer of polyethyleneinto which only alkyl acrylate has been copolymerized, wherein thecombination of the ethylene-glycidyl copolymer and the ethylene-acrylatecopolymer is no more than 5 weight percent based on the modifiedpolyester composition.
 30. A modified polyester composition comprising apolyester containing an acid component containing 80 mol % of anaromatic dicarboxylic acid and a glycol component containing 80 mol % ofaliphatic diol, a modified polyolefin and 5 to 35 weight percent basedon the modified polyolefin of polyethylene into which only alkylacrylate has been copolymerized, wherein the modified polyestercomposition comprises no more than 5 weight percent of the total of themodified polyolefin and the ethylene-acrylate copolymer.